In many soil separators used to screen out coarse material from finer soils, feeding of soil to be separated is accomplished by dumping the material from a shovel of an excavating vehicle onto a grate or screen of the soil separator. The separators which are involved in this invention are also used to separate various excavation and construction materials, and various waste materials, particularly land-fill waste and compost. The separating elements may be grates, screens or a series of rods, which may be cantilevered and may be moving or vibrating.
Soil separators traditionally have employed an inclined screen having a high end and a low end onto which the soil to be separated by screening is loaded gradually such that the larger rocks and aggregate roll off the low end of the screen and finer materials pass downwardly through the screen at a gradual feeding rate to prevent clogging. Improved soil separators such as "Screen All" soil separators, a registered trademark of The Read Corporation, are disclosed in U.S. Pat. Nos. 4,197,194, 4,237,000, 4,256,572, and 5,082,555 and are hereby incorporated by reference. These soil separators have a box like housing, and, in addition to an upper coarse mesh screen, employ two lower slanted screens connected to a vibrator for shaking soil material loaded on the upper screen and contained thereon for screening by side panels and a high end panel, the low end being open. The very coarse material loaded on the upper screen is screened out initially by the slanted upper coarse mesh screen. The large particles pass from the upper section of the screen downwardly along the slanted surface of the upper screen and fall off the lower end, to be collected. The less coarse material passes through the upper screen and encounters shaking action of the lower slanted screens which accelerate the process of separating, permitting a faster rate of loading, with the finer materials passing downwardly to a segregated bin under the housing, accessible for removal from the high end. Because the low end of the coarse screen is open for releasing coarse materials, it is not feasible to dump a large load of soil on the slanted screen. This is because the fine material would pass off the lower end with the coarser material and become co-mingled with the coarse soils.
The loading and feeding of the soil separators may be done by a conveyor or input hoppers, or more frequently, by dumping soil material onto the top screen, frequently positioned in a hopper, from the shovel of an excavating-type vehicle, like a front end loader. When an excavating vehicle, such as a pay loader, is employed, it is necessary to feed the soil material at a controlled rate onto the upper inclined grate, from which the soil material is funneled onto the grate by upwardly inclined side panel sections, and the high end funnel surface, which serve as a hopper. This feeding operation requires time and a certain degree of skill on the pay loader operator's part and therefore, ties up the use of very expensive equipment at considerable cost and inconvenience.
It was therefore desirable to provide for an improved and effective soil feeding mechanism, and to provide a soil feeding mechanism in combination with a soil separator to provide for a controlled rate of loading and improved separation of finer soils and to a method of feeding soils, to be separated, into a soil separator employing the improved soil feeding mechanism.
As was clearly established by the system described in the READ patent U.S. Pat. No. 5,082,555, an improvement to a material feeder system will increase the level of productivity that could be expected when using the material feeder in conjunction with a vibratory material separating apparatus. With the addition of a material feeder the desired effect is to gain benefit through improvement in the quality of separation in the product being screened as well as time savings through the utilization of the material feeder to deliver the material to the screening surface. Conventionally the material to be separated would be delivered to the vibratory material separating apparatus by way of a front end bucket type of loader which would empty its contents directly onto the screening surface. The key to the quality of the separation process and efficiency of the overall operation is tied into the rate at which the loader feeds the material onto the screening surface and how frequently the loader delivers a bucket of material to be separated. Without a material feeder the front end bucket loader would arrive at the vibratory material separating apparatus with a full bucket of unseparated material raised into a position ready to empty its contents over the screening surface. This process would require that the loader remain at the separator and gradually empty the material from the bucket onto the screening surface. The technique used and the rate at which the bucket is emptied is directly related to the composition of the material in the bucket. The object of the material feeder is to decrease the time that the loader must spend at the vibratory material separating apparatus. The time lost gradually emptying the loader bucket could be more effectively applied to the retrieval of more unseparated material. This more efficient use of time would result in more loading and unloading trips or cycles which would increase the productivity of the manpower and equipment required for the material separating process.
It was the intent of this improvement to enhance the performance of the material feeder system by facilitating the discharge of material from the bucket to the screening surface of the vibratory material separating apparatus. The benefits of using a material feeder system can be significant when compared to productivity levels achieved using the front end bucket loader as the sole means of delivering unseparated material to the screening surface. The means currently in use for creating a consistent flow of material from the feeder assembly is rotation of the feeder about an axis which gradually exposes more material to an unsupported position above the screening surface whereby gravity is allowed to pull material out of the feeder onto the screening surface for separation. This method employs a pivot point and hydraulic cylinders mounted between the feeder assembly and the vibratory material separating apparatus to achieve the rotation of the feeder. There are also other hydraulic components incorporated in the system to control the speed at which the (full) feeder assembly rotates upward or raises to empty the contents, as well as controls to regulate the speed of the (empty) feeder rotating downward to the lower "ready to receive material" position. These speed controls are located within the hydraulic control module which also features components to operate other aspects of the feeder system. The overall hydraulic system exists on the equipment as the means for operating the various functions required for a vibratory material separating apparatus. Therefore it is the most convenient method of driving any auxiliary equipment such as the material feeder system.
Other specific aspects of the material feeder system include a secondary hydraulic pump which is mounted to the primary hydraulic pump used to drive the hydraulic of the vibratory material separating apparatus. The secondary pump drives the hydraulic cylinders which are used to pivot or raise the feeder assembly to allow the unscreened material to be delivered onto the screening surface. The oil that is pumped from the secondary hydraulic pump is directed to the hydraulic control module where it is routed to either the hydraulic cylinders to raise the feeder assembly or back to the hydraulic oil reservoir when no cycle start signal has been received. The secondary hydraulic pump is sized based upon the requirements of the hydraulic cylinders to lift the feeder assembly when it is at its maximum weight capacity of unscreened material. Within this module there is an electrical solenoid which acts as a gate for routing the oil to either of its destinations. The solenoid receives its instructions from an electrical control panel which contains the circuitry for starting a material feeder cycle as well as circuits for an emergency abort of a cycle which signals the electrical solenoid to divert the flow of oil from the hydraulic cylinders and route the oil back to the hydraulic reservoir.
There is also a mechanical trigger which is activated by the front end bucket loader after it empties the unseparated material into the feeder assembly. The trigger initiates the cycle through the electrical control panel which instructs the electrical solenoid in the hydraulic control module to route the oil to the hydraulic cylinders in order to pivot or raise the feeder assembly to allow the unscreened material to be delivered to the screening surface. In order to achieve the highest degree of material separation, it is important that the volume of unscreened material present on the screening surface at any given time not exceed the ability of the vibratory screening apparatus to separate that material. The method currently in use to accomplish this is the slow pivoting rotation of the full feeder assembly into the raised position. This gradual movement of the feeder assembly results in a limited degree of metered discharge of the unseparated material from the feeder assembly onto the screening surface.
This method produces unpredictable results often manifested as a clumping action where the material remains in the feeder assembly while pivoting upward until the forces of gravity on the unscreened material overcome the friction between the material and the feeder assembly which causes the contents of the feeder to empty onto the screening surface in one mass or clump. The tendency of the material to adhere to the feeder assembly and also to itself is common and due in large part to the inconsistent composition and moisture content of the unscreened material. This phenomenon which drastically reduces the efficiency of the vibratory material separating apparatus is the most significant disadvantage to using a material feeder system and therefore the problem most in need of a solution. Since an effective feeder system could offer such an increase in productivity through manpower and equipment an improvement to the method currently in use is important.
A method that has been used to overcome these problems is the installation of a hydraulically driven vibrator onto the feeder assembly. Such a system is described in U.S. Pat. No. 5,232,098, to St. Pierre et al., filed on Mar. 25, 1992, and issued on Aug. 3, 1993. However the effect of vibration on the unscreened material is often as much of a hinderance as it is a help. In an effort to move material out of the feeder assembly the vibrator also compacts or jells the material that is in the feeder which increases the tendency of the material to adhere to itself and the feeder assembly which again produces a clumping action as the unscreened material is delivered to the screening surface. Delivering a full or near full load of unscreened material onto the screening surface in one mass or clump greatly reduces the volume and quality of separated material that the vibratory material separating apparatus can process and negates any benefits that an effective material feeder system could offer. Also the additional cost in componentry and maintenance to drive and control the vibrator make its limited potential benefit a poor choice for increasing the effectiveness of a material feeder system.
It is therefore a primary purpose of the present invention to provide an improvement in a soil feeder apparatus and to a soil feeder apparatus in combination with a vibratory material separating apparatus and to a method of improving the feeding of unscreened material onto a vibratory material separating apparatus.
It is furthermore a purpose of the present invention to provide an efficient and cost effective means of discharging unscreened material from a material feeder onto the screening surface of a vibratory material separating apparatus with a method that will allow for the efficient separation of unscreened material into separate stockpiles based upon the physical size of the objects within the screened material.